In the realm of electronics manufacturing, adherence to industry standards is crucial to ensure high-quality products and reliable performance. One such set of widely recognized standards is the IPC (Association Connecting Electronics Industries), which plays a pivotal role in defining guidelines for printed circuit boards (PCBs). Within these standards, Class 2 and Class 3 classifications hold particular importance, as they help determine the level of quality and reliability required for electronic boards used in different applications. This article aims to elucidate the key differences between Class 2 and Class 3 electronic boards, as well as provide an overview of IPC and its significance in the electronics industry.

Ucreate has been dedicated in PCB and PCBA industry for more than two decades. As a circuit board manufacturer, we are often asked with many questions. One of them regularly asked is the difference between IPC Class 2 and IPC Class 3. Today, let Ucreate help you go through with IPC.

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What is IPC?

IPC, short for the Association Connecting Electronics Industries, is a global trade association that develops and publishes industry standards for the design, production, and testing of electronic components and assemblies. Established in 1957, IPC has been instrumental in promoting excellence and consistency across the electronics manufacturing industry. IPC standards cover a wide range of aspects, including PCB design, material selection, assembly, and testing, among others.

IPC standards are periodically revised and updated to keep pace with advancements in technology, ensuring that manufacturers adhere to best practices and provide customers with reliable and high-quality electronic products.

Understanding PCB Classes

IPC standards classify PCBs into three main classes: Class 1, Class 2, and Class 3. These classes are used to specify the quality, reliability, and performance requirements of a PCB based on its intended application and the potential consequences of failure.

Class 1: Basic consumer electronics

Class 1 PCBs are designed for general consumer electronics and applications where the functionality and reliability requirements are relatively low. The lowest PCB quality level are used in products where performance is not critical, and failure would not lead to significant consequences.

Class 1 PCBs are commonly found in toys, basic consumer electronics, and other disposable or low-cost items.

IPC Class 2: Dedicated service electronic products

Class 2 boards have higher reliability and extended life. They follow more stringent standards than Class 1 but allow some cosmetic imperfections. Here, uninterrupted service is preferable, but not critical. Class 2 products aren’t exposed to extreme environmental conditions. The board is expected to run continuously but its operation is not extremely critical. These kinds of boards are implemented in your laptops, smartphones, tablets, communication equipment etc.

Class 2 PCBs find applications in household appliances, automotive electronics, and most commercial electronics.

IPC Class 3: High-performance electronic products

Class 3 represent the highest quality PCBs and reliability standards.

Class 3 electronic boards must provide uninterrupted service even in harsh operating environments. There can be no equipment downtime High levels of inspection and testing are performed on these boards with stringent standards. This makes them highly reliable. Apart from complying with Class 3 standards, these boards should also meet the additional requirements mentioned in the lPC 6012E document. It sets benchmarks for the boards used in military, medical, and automotive applications.

Class 3 PCBs in such as aerospace, medical devices, military equipment, and other high-reliability systems.

What are the differences between Class 2 and Class 3 in PCB assembly?

The major differences between Class 2 and Class 3 are found in component placement for surface-mount components, cleanliness requirements based on residual contaminants or the assemblies, plating thicknesses as defined in plating through-hole and on the surface of PCBs.

During assembly, SMD might be slightly placed off the pad. This is what we call a visual defect since it does not usually affect electrical and mechanical performance. It, therefore. does not matter for Class 2 circuit boards. However. Class 3 does not accept any imperfection and this type of assembly misstep will cause the circuit board to fail the inspection.

Class 2 PCBs may use standard or economical materials that meet the necessary functional requirements.

Class 3 PCBs typically demand high-quality materials with enhanced performance characteristics to ensure long-term reliability and stability.

The solder joints for Class 3 boards should not have any voids, cracks, or defects. However, minor visual defects are allowed in Class 2.

Soldering defects on a circuit board

The amount of barrel fill required for through-hole leads is 50% for Class 2 and 75% for Class 3. As it can be delicate to get the paste into small plated through-holes(PTH), Sierra’sadvice is to design your PTH 15 mil over the diameter of the lead. This way, you will have 7.5 mil on each side which will make it easier for the paste to fill the barrel.

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Inspection difference

General inspection methods for checking Class 2 and 3boards include visual, AO, X-ray, solderability, and electrical testing. However, the specs will be more stringent for Class 3 PCBs. Additional testing like micro-section analysis and environmental tests like stress, pressure, vibration, and burn-in tests are also conducted.

After the end-use of the product, the degree of inspection is what should take into account when choosing which category your PCB should fall into. Keep in mind that inspection is one of the factors that drive up the cost when an assembly goes from Class 2 to Class 3.

IPC standards are integral to the electronics industry, providing guidelines for the design, production, and testing of electronic components and assemblies. The classification of PCBs into Class 2 and Class 3 plays a vital role in ensuring that products meet specific quality and reliability requirements based on their intended applications. While Class 2 PCBs suffice for many consumer electronics and commercial products, Class 3 PCBs are indispensable in critical systems where failure can have severe consequences. By adhering to IPC standards and understanding the distinctions between Class 2 and Class 3 PCBs, manufacturers can confidently produce electronics that meet the demands of various industries and applications.

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